In a mobile terminal such as a mobile phone, a personal handy phone system (PHS), and a personal digital assistant (PDA), a tendency toward downsizing and thinning is being accelerated. In order to achieve the downsizing and thinning of such mobile terminals described above, development has been promoted about downsizing and thinning of functional components for forming the same, thinning of a printed circuit board on which the functional components are mounted, downsizing of an antenna system, a reduction in wall thickness and thinning of a casing accommodating the functional components, the printed circuit board, etc., and the like. Under the circumstances, the thinning of a switch structure is also being promoted. However, it should be noted that the thinning tends to impair uniformity of switch illumination.
FIGS. 21 and 22 are sectional views of conventional mobile terminals. In particular, the conventional mobile terminal as shown in FIG. 22 is generally formed by stacking, in a thickness direction, a structure 501, switch buttons 525, a key sheet 502, conductors 524, a switch substrate 555, and a substrate 504 on which electronic components 503 are mounted. A predetermined number of LEDs 560 are mounted on the switch substrate 555, and emit light horizontally or vertically. The switch substrate 555 should be arranged on a flat plane, and the LEDs 560 should be situated outside of the conductors 524.
The structure 501 has a large number of through-holes, through which the switch buttons 525 are projected. Wiring patterns 522A and 522B are formed on an upper surface of the switch substrate 555. The conductors 524 are formed by a conductive material elastically deformable and have outer peripheral edges electrically connected to the wiring pattern 522A. When the switch buttons 525 are depressed, the conductors 524 are caused to undergo elastic deformation via the key sheet 502, and the central portions thereof come into contact with the wiring pattern 522B. As a result, the wiring patterns 522A and 522B become electrically conductive with each other. This makes it possible to input predetermined information. The LEDs 560 are caused to emit light with timing with which the predetermined information is input. The light from the LEDs 560 passes peripheral clearances, and is scattered from a horizontal direction to a vertical direction to be output through the key sheet and the switch buttons.
Next, FIG. 21 shows a structure 101 as disclosed in Patent Document 1 (JP 2002-23921 A). The structure 101 has protrusions 112 provided on an upper surface, a surface-emission type luminous sheet 160 placed on a wiring sheet on which conductors 124 are mounted and downwardly directed toward the protrusions 112. Surface light emission is effected by an organic EL fluorescent material (OLED). Solely the plurality of protrusions 112 are arranged on the structure 101, and no members supporting the wiring sheet are provided around the protrusions 112. Further, this structure is featured by an illumination region separate from the wiring pattern on the wiring sheet. When the switch buttons 125 are depressed, the switch buttons 125 push down the conductors 124, and denting click operation is effected with the protrusions 112, thereby operating the switch circuit. Description in Patent Document 1 is restricted to the illuminating function, and nothing is disclosed therein regarding switch click characteristics involved and an influence of the illumination on the periphery.